CLIAMS:CLAIMS
We Claim:

1 An overflow valve (100) in a fuel control unit comprising:
an inlet (105);
a valve member (110); and
an outlet (115)
characterized in that
a return line connector (120) in fluid connection with said valve member and connected to the outlet such that said return line connector is coaxial to said inlet and said outlet.

2 The overflow valve (100) as claimed in claim 1, wherein said return line connector (120) is fitted in said outlet using a press-fit contact.

3 A return line connector (300) in a fuel control unit comprising:
an inlet (305);
an outlet (310); and
a channel (315) formed between said inlet (305) and said outlet (310)
characterized in that
an overflow valve (400) comprising a plurality of overflow valve components located in said channel (315) of the return line connector (300).

4 The return line connector (300) as claimed in claim 3, wherein said overflow valve components comprise a valve member (405), a spring (410) and a plug (415).

5 The return line connector (300) as claimed in claim 3 further comprising:
at least two holes to enable flow of fuel from said inlet (305) of said return line connector (300) to said outlet (310) of said return line connector (300);

6 An overflow valve (100) in a fuel control unit, said overflow valve (100) comprising:
a valve member (110) and a return line connector (120);
characterized in that
a bush (210) adapted to house said valve member (110), wherein said bush (210) is located along a port (235);
a spring (220) having a first end and a second end, the first end being in contact with said valve member (110); and
a plate (225) fixed to said return line connector (120), wherein said plate (225) is used to mount said spring (220) and is in contact with said second end of said spring (220).

7 The overflow valve (100) as claimed in claim 3, wherein said bush (210) comprises an aperture (240) that is adapted to allow excess fuel to flow to said return line connector (120).

8 The overflow valve (100) as claimed in claim 3, wherein said open position corresponds to movement of said valve member (110) to unblock said aperture (240), located in said bush (210), for allowing excess fuel to flow to said return line connector (120) through said aperture (240).

9 The overflow valve (100) as claimed in claim 3, wherein said closed position corresponds to movement of said valve member (110) for closure of said aperture (240) located in said bush (210).

10 A fuel control unit, for controlling flow of fuel to a high pressure fuel pump, said fuel control unit comprising:
a housing (130), a fuel metering unit (135), an overflow valve (100) and a return line connector (120);
characterized in that
said return line connector (120) located coaxially with respect to inlet and outlet of said overflow valve (200).

11 The fuel control unit as claimed in claim 7, wherein said return line connector (120) is connected to said housing (130) using a press-fit contact. ,TagSPECI:Field of the invention
[001] This invention relates to a fuel control unit, for controlling flow of fuel to a high pressure fuel pump.

Background of the invention
[002] A fuel control unit generally between a fuel tank and a high pressure fuel pump, is used for controlling quantity of fuel delivered into the high pressure fuel pump. The fuel control unit comprises a housing that accommodates a fuel metering unit and an overflow valve.

[003] Fuel from the fuel tank is delivered to the fuel metering unit through a fuel inlet line that is connected to the housing. Axis of the fuel inlet line is generally perpendicular to the axis of the fuel metering unit. The fuel metering unit meters the fuel using a solenoid valve assembly so that appropriate amount of fuel is delivered to the high pressure fuel pump.

[004] Upon metering, excess fuel is led to a return line connector through the overflow valve. Height of a screw plug, comprised in the overflow valve, defines an opening pressure of the overflow valve. The opening pressure of the overflow valve defines a pressure value, of the excess fuel, at which the overflow valve opens to lead the excess fuel into the return line connector. A particular screw plug height corresponds to a specific opening pressure. However, to obtain different opening pressures, different screw plugs with varying heights should be used. Therefore such an assembly limits flexibility to vary the opening pressure. Hence, a technique to address this issue is required.

[005] Also, the return line connector is positioned such that the axis of the return line connector is perpendicular to the axis of the overflow valve. Such an assembly of the fuel control unit requires large number of connecting holes in the housing leading to high machining cost. Also, such an assembly is massive and consumes excess space since the overflow valve and the return line connector are positioned in varying planes. Hence need for a compact assembly of the fuel control unit is required.

Brief description of the accompanying drawings

[006] Figure 1 illustrates a return line connector in a fuel control unit, in accordance with one embodiment;

[007] Figure 2 illustrates an overflow valve in a fuel control unit, in accordance with one embodiment; and

[008] Figure 3 illustrates a fuel control unit in accordance with one embodiment.

Detailed description
[009] An overflow valve in a fuel control unit, in accordance with one embodiment is disclosed. The overflow valve includes an inlet, a valve member and an outlet. The overflow valve further includes a return line connector in fluid connection with the valve member and connected to the outlet such that the return line connector is coaxial to the inlet and the outlet.

[0010] The overflow valve is adapted to return excess fuel, accumulated in a housing of the fuel control unit, into the return line connector. The excess fuel from the fuel control unit is initially led into the inlet of the overflow valve. Fuel from the inlet is supplied to the return line connector through the valve member. In one example, the valve member can include a ball. The valve member opens when the fuel entering into the inlet has a pressure beyond a threshold value, thereby supplying the excess fuel into the return line connector.

[0011] The return line connector is fitted to the outlet using a press-fit contact. By using a press fit contact pressure of the fuel that is required for opening the valve member can be controlled. Such pressure can also be referred to as opening pressure of the valve member. Hence, such an assembly provides for flexible variation of the opening pressure, thereby avoiding usage of different screw plugs, of varying heights, for obtaining desired opening pressure.

[0012] Figure 1 illustrates a return line connector 300 in a fuel control unit, in accordance with one embodiment. The return line connector 300 includes an inlet 305, an outlet 310 and a channel 315. The return line connector 300 is characterized by an overflow valve 400 located in the channel 315 of the return line connector 300. The overflow valve 400 is adapted to block and unblock at least one hole present in the return line connector 300.

[0013] The return line connector 300 further includes at least two holes to enable flow of fuel from the inlet 305 of the return line connector (300) to said outlet (310) of the return line connector (300).

[0014] Excess fuel present in the fuel control unit reaches the inlet 305 of the return line connector 300. When pressure of the fuel, entering the inlet 305, exceeds a threshold value, the overflow valve 400 is adapted to unblock a first hole 320 of the return line connector 300.

[0015] The overflow valve 400 comprises a plurality of overflow valve components. The overflow valve components include a valve member 405, a spring 410 and a plug 415 that are located in the channel 315 of the return line connector 300. In one example, the valve member 405 may include a ball. One end of the valve member 405 is in contact with the inlet 305 and other end of the valve member 405 is in contact with the spring 410. The spring 410 is mounted on the plug 415 that is fixed firmly in the channel 315. Working of the overflow valve 400 is explained in detail in the following paragraphs.

[0016] The valve member 405 is adapted to compresses the spring 410 thereby unblocking the first hole 320 when the fuel of pressure beyond a threshold value is incident on the valve member 405.

[0017] The first hole 320 forms a fluid path for the fuel to flow from the inlet 305 to a port 330 of the fuel control unit. Further, a second hole 325 included in the return line connector 300 forms a fluid path for the fuel to flow from the port 330 of the fuel control unit to the outlet 310 of the return line connector 300. Fuel flowing through the outlet 310 is thereby returned to a fuel tank.

[0018] The threshold value of the fuel pressure that is required for unblocking the first hole 320 can be varied based on extent to which the plug 415 is press-fitted into the channel 315. Therefore the return line connector 300 in accordance with this embodiment enables alteration of opening pressure by merely varying the extent which the plug 415 is press-fitted into the channel 315.

[0019] Figure 2 illustrates an overflow valve 100 in a fuel control unit, in accordance with one embodiment. The overflow valve 100 includes the valve member 110 and the return line connector 120. In one embodiment of this disclosure, the return line connector 120 is coaxial to the overflow valve 100. The overflow valve 100 is characterized by a bush 210 adapted to house the valve member 110. The bush 210 is located along a port 235. The bush 210 further includes an aperture 240. Further, the overflow valve 100 includes a spring 220 having a first end and a second end. The first end is in contact with the valve member 110. The overflow valve 100 further comprises a plate 225 fixed to the return line connector 120 on one end. The plate 225 is used to mount the spring 220 and is in contact with the second end of the spring 220.

[0020] The bush 210 is placed in the port 235 and houses the valve member 110. The valve member 110, in one example, can be a ball. The bush 210 is adapted to receive excess fuel from a fuel inlet line of the fuel control unit. The excess fuel received, is incident on the valve member 110.

[0021] The valve member 110, located within the bush 210, is adapted to compress the spring 220, when pressure of the fuel, striking the valve member 110, exceeds a threshold value. In one example, the pressure of the fuel begins to increase when the fuel inlet line continues to supply fuel even after a fuel metering unit has ceased the process of metering the fuel.

[0022] The valve member 110 moves between an open position and a closed position against force of the spring 220, as the first end of the spring 220 is in contact with the valve member 110. The spring 220 may attain a compressed state when the valve member 110 is moved to the open position and the spring 220 may attain a free state when the valve member 110 is moved to the closed position. The spring 220 is mounted on a plate 225 by placing the second end of the spring 220 on a base of the plate 225.

[0023] Movement of the valve member 110 such that the valve member 110 is moved to the open position leads to unblocking of the aperture 240 in the bush 210. The valve member 110 is moved to the open position when the pressure of the fuel exceeding the threshold value strikes the valve member 110. Such pressure that enables movement of the valve member 110 to the open position is also referred to as opening pressure of the valve member 110. Unblocking of the aperture 240 allows the excess fuel, striking the valve member 110, to flow to the return line connector 120 through the aperture 240 along the channel 235. The excess fuel from the return line connector 120 is thereby delivered to the fuel tank.

[0024] Further, when pressure of the excess fuel, along the channel 235, does not exceed the threshold value, the valve member 110 moves to the closed position. Movement of the valve member 110 to the closed position leads to blocking of the aperture 240. Hence, no fuel flows into the return line connector 120.

[0025] The plate 225 is adapted to position the spring 220 such that the spring 220 is in line with the channel 235, the overflow valve 100 and the return line connector 120. The plate 225 is also connected to the return line connector 120, as shown in Figure 2, such that the overflow valve 100 and the return line connector 120 are coaxial with respect to each other. In one embodiment, the return line connector 120 is connected to the plate 225 at the base of plate 225 using a press-fit contact. Various other means of connection can also be used for connecting the return line connector 120 to the base of the plate 225.

[0026] Pressure of a threshold value as mentioned in the preceding paragraphs can be defined based on pre-tension length of the spring 220. The pre-tension length of the spring 220 may be defined as length of the spring having a corresponding tension value such that fuel having a pressure of the pre-defined threshold value is required to overcome the tension value and compress the spring 220 for unblocking the aperture 240 thereby leading the excess fuel into the return line connector 120.

[0027] The pre-tension length of the spring 220 can be varied based on a press-in length of the return line connector 120. The press-in length of the return line connector 120 is defined as an extent to which the return line connector 120 is pressed into the channel 235 using the press-fit contact.

[0028] In one example, if the press-in length is large, then the pre-tension length of the spring 220 decreases, thereby increasing the pre-defined threshold value of the pressure of the fuel. Hence, large pressure is required to move the valve member 110 for unblocking the aperture 240. Therefore, the opening pressure of the valve member 110 can be varied by merely varying the press-in length of the return line connector 120, thereby providing a flexible design for opening pressure variation. Also, this assembly eliminates need for using screw plugs of different heights for varying the opening pressure.
[0029] Figure 3 illustrates a fuel control unit, in accordance with one embodiment. The fuel control unit includes a housing 130, a fuel metering unit 135, the overflow valve 100 and the return line connector 120. The return line connector 120 is being located coaxial to the overflow valve 100.

[0030] The housing 130 houses the fuel metering unit 135 and the overflow valve 100. A fuel inlet line 140 is connected to an input port of the housing 130 and may have an axis perpendicular to the axis of the fuel metering unit 135 as shown in Figure 3.

[0031] Fuel from a fuel tank enters into the fuel metering unit 135 through the fuel inlet line 140. The fuel metering unit 135 meters the fuel using a solenoid operated control valve assembly. Metered fuel is supplied to the high pressure fuel pump through the outlet line 125.

[0032] In one scenario, the fuel inlet line 140 may continue to supply fuel even after the fuel metering unit 135 ceases to meter the fuel. In such cases, excess fuel may get accumulated within the housing 130. Due to such accumulation pressure of the fuel increases. When the pressure exceeds a threshold value, the excess fuel is led to the return line connector 120 through the overflow valve 100 along the channel 235. The working of the overflow valve 100 and its components are explained in detail in conjunction with Figure 1 and Figure 2.

[0033] In one embodiment, the return line connector 120 is fitted into the overflow valve 100 using a press-fit contact such that the return line connector 120 is coaxial to the overflow valve 100. Various other contact means may also be used for integrating the overflow valve 100 with the return line connector 120.

[0034] In another embodiment, the return line connector 120 may be connected to a return port of the housing 130. The return line connector 120 is coaxially aligned with respect to the overflow valve 100. The excess fuel the return line connector 120 is thereby returned to the fuel tank. Arrangement of the return line connector 120 coaxially with respect to the overflow valve 100 results in reduced space consumption by the fuel control unit. Further, such an assembly reduces number of connecting holes in the housing thereby reducing machining cost.

[0035] It must be understood that the embodiments explained above are only illustrative and do not limit the scope of the disclosure. Many modifications in the embodiments with regard to type of the overflow valve and means of connecting the return line connector to the overflow valve are envisaged and form a part of this invention. The scope of the invention is only limited by the claims.